How to Accurately Calculate the Number of Pagination Pages?

Calculating Pagination Page Count with Integer Division Rounding

When displaying paginated data, determining the number of pages required can involve rounding up the result of integer division. This becomes particularly relevant when working with integers in languages like C# or Java.

Consider a scenario where you have a certain number of items that you want to display in fixed-sized chunks or pages. The challenge lies in calculating the total number of pages needed.

For instance, if you have 100 items and want to display 20 items per page, how many pages would be required? Using integer division alone would result in 100 / 20 = 5. However, since the last page may not be fully filled, you need to round up to 6 pages to ensure all items are displayed.

An elegant solution to this problem, as discovered by Roland Backhouse in his book "Number Conversion," involves using the following formula:

pageCount = (records recordsPerPage - 1) / recordsPerPage

This formula effectively rounds up the result of integer division. It adds 1 to the sum of the total records and the records per page and then divides by the records per page. In our example, this translates to pageCount = (100 20 - 1) / 20 = 6.

By applying this formula, you can accurately determine the number of pages needed to display a given number of items in fixed-sized chunks, ensuring that all items are accounted for.

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